Method and apparatus for annealing



Oct. 17, 1944. E. ALLEN ET AL 2,360,633

METHOD AND APPARATUS FOR ANNEALING Filed Aug. 23, 1943 v INVENTORS 145.14M? and d L W/I/fffl Patented Oct. 17, 1944 UNITED STATES PATENT OFFICEMETHOD AND APPARATUS FOR ANNEALING Application August 23, 1943, SerialNo. 499,660

Claims. Cl- 26344) This invention relates to the art of annealing and,in particularly, to the annealing of flatrolled material such as stripor sheets.

In recent years, the use of cover-type annealing furnaces has becomevery widespread. Generally speaking, such furnaces comprise a baseadapted to receive the charge to be annealed, i. e., strip in coils orsheets in a pile, an inner or protective cover disposed over the chargeand a heating cover adapted to be lowered over the inner cover andprovided with heating means. In some furnaces the heating means aremounted inside the inner cover. In the usual operation a single outercover cooperates successively with a plurality of bases, being disposedthereon in turn during the heating portion of the annealing cycle.Heretofore, it has been the practice after the charge has been raised tothe desired temperature, to permit the cooling thereof by loss of heatto the atmosphere. While this resulted in a slow cooling which isdesirable, the time required for the charge to cool to a temperature atwhich the inner cover may be safely removed in such as to impose aserious limitation upon the amount of material it is possible to processwith a given number of bases and a single outer cover.

As a mattter of fact, the charge may be cooled at rates considerablyhigher than that at which it cools by loss of heat to the atmosphere,without impairing the quality of the product. Attempts have accordinglybeen made to apply artificial cooling to reduce the over-all annealingtime. So'far as we are aware, all such expedients have been of themakeshift variety and have not been wholly successful from thestandpoint of actual operations.

We have invented a novel method and apparatus for annealing whereby thelength of the cooling stage of the annealing cycle is reduced to abouthalf the time required for cooling of the charge by loss of heat to theatmosphere. In a preferred embodiment and practice of our invention, weprovide a cooling jacket adapted to be disposed over the inner cover.after removal' of the outer cover therefrom. By means of the jacket, wecreate a descending shower or curtain of liquid surrounding the coverbut maintained out of contact therewith. We also blow air repeatedlythrough the descending curtain of liquid thereby causing partialevaporation thereof with the result that the inner cover and the chargeenclosed thereby are subjected to a pronounced cooling effect.

Further details, novel features and advantages of the invention will bemadeapparent by the following detailed description and explanation whichrefer to the accompanying drawing illustrating preferred embodiments ofthe apparatus contemplated by our invention. In the drawing,

Figure 1 is a central vertical section through one formv of base for acover-type furnace, the inner cover thereon with built-in heatingelements, and the cooling jacket of our invention disposed thereover;

Figure 2 is a portion of Figure 1 to enlarged scale; and

Figure 3 is a partial section similar to Figure 1 showing a form ofcooling jacket adapted to cooperate with a slightly different type ofbase.

Referring now in detail to the drawing and, for the present, to Figures1 and 2 our invention, in one form, comprises a coolingjacket ID adaptedto be disposed over an inner cover ll resting on a charge-supportingbase l2 and enclosing a charge 13 disposed on the base, in theillustrated example, a coil ofstrip. The inner cover H and base l2 areillustrated and described in detail in'Woodson Patent No. 2,249,- 411and .it is therefore unnecessary to explain their construction furtherthan to state that the base is composed of refractory brick laid on anenclosure fabricated from plate and structural members, and havinga'charge-receiving casting l4 thereon while the inner cover is formedlargely of metal plate, having the lower portion of its wall lined withrefractory brick l5 and provided with radiant heating tubes l 6 mountedinteriorly thereof. In horizontal section, the cover II is circular, toconform with the-shape of the charge and the base is of similar shape inplan. Both may be rectangular, however, if annealing sheets in piles.

The furnace cover adapted to cooperate With the inner cover II and basel2,'as shown in the Woodson patent, comprises simply an open-bottomedenclosure lined with refractory brick. The furnace cover is supported ona sealing flange depending from the bottom edge thereof adapted to bereceived in a channel I! extending around the inner cover I l.

The cooling jacket I!) is also an open-bottomed enclosure the lower edgeof which is adapted to rest on the bottom of the channel [1. The jacketIll comprisesa generally cylindrical outer wall 18 having a top H!thereon-provided with a central hole 2!]. The jacket also includes apartial inner wall 2| of generally frusto-conical shape, the lower edgeof which is secured to the bottom edge of the outer wall I 8. Above thebottom edge, the inner wall is spaced inwardly from the outer wall.Posts Zla secured to the wall 2| support a distributor cone 22 the outeredge of which overhangs the upper edge of the wall. A substantiallycylindrical bafile wall 23 is spaced inwardly from the outer wall andextends downwardly from the top l9, terminating above the junction ofthe inner and outer walls.

the posts 2|a to the baffle wall. Frusto-conical baffles 25 and 26 aremounted, respectively, on the baflie wall 23 and the post 2|a invertically spaced relation, the two types of baffles being oppositelyinclined and disposed in alternating relation in order to causecascading of a curtain of liquid descending from the cone 22 within thebaffle Wall 23, and into the space between the inner wall 2| and theouter wall l8. The inner wall 2| has notches 21 spaced circumferentiallythereof through which liquid discharged downwardly of the cooling jacketmay flow into the channel H. An overflow pipe or other equivalent means(not shown) is provided for conducting the water to a. cooling sump orto the sewer.

An external spray head 28 in the form of a circular pipe having holestherein is mounted on brackets 29 centrally of the cone 22. Liquid suchas water, when supplied to the head 28 from a suitable source through apipe 30, runs down the distributor cone and over the edge thereofforming a descending shower or curtain distributed substantiallyuniformly around the circumference of the jacket ID. The liquid strikesthe top retarder plate 24 and on passing through the holes thereof,comes in contact with the baffles 25 and 26 successively and thuscascades downwardly. This sequence is repeated as the liquid continuesto fall toward the bottom of the jacket. 7

An internal spray head 3| similar to the head 28 connected to the sourceof liquid by pipe 3| may be employed to direct a uniformly distributedspray on top of the inner cover during the final portion of the coolingstage of the cycle, if desired.

A cage 32 mounted on the top I9 is composed of posts 33 and annular bars34 secured thereto in vertically spaced relation. A top 35 surmounts thecage and is provided with a lifting eye 36. Diagonal braces 31 spacedcircumferentially of the jacket extend from the top 35 to the-outer edgeof the top IS.

A motor 38 is disposed centrally of the cage 32, being carried on anysuitable form of suspension such as a hanger 39 depending from the top35, and is provided with a fan 39 adapted to drive air downwardlythrough the opening 20 in the top I9. A conical b aille 40 is mounted onbrackets 4| extending upwardly from the spray head 28. The bafile 40 andthe distributor cone 22 guide the air entering the jacket downwardlywithin the baffle wall 23. The air delivered by the fan is drawn intothe cage 32 between the bars thereof. The air descending through thejacket strikes the retarder plate 24 and the bafiies 25 and 26. Thelatter cause the air to pass repeatedly through the descending curtainor cascade of liquid, thereby evaporating a substantial portion of theliquid and exerting a strong cooling action. On reaching the bottom edgeof the baflie wall 23, the air passes upwardly through the space betweenthe baffle wall and the outer wall IB through outlet ports 4| spacedcircumferentially of the latter near the upper edge thereof.

While the normal functioning of the apparatus described above and themethod of our invention will doubtless be understood from what hasalready been said, a complete annealing cycle will now be described forthe sake of completeness.

When the base I2 is ready to receive a change to be annealed, i. e.,when the cooling jacket, inner cover and previous charge have beenremoved, the next charge is placed on the base, the inner cover loweredthereover and the outer cover placed on the inner cover. The radianttubes l6 are then fired for the period of time necessary to bring thecharge up to the desired annealing temperature, e. g., 1100 F. When thecharge has been raised to this temperature, the outer cover is removedand firing of the tube I6 is discontinued. The cooling jacket I0 is thenlowered over the inner cover and the supply of liquid for the spray head28 is turned on. While we prefer to use Water as the liquid to beevaporated, any other suitable liquid may be used instead. The motor 38is then started to cause air to be blown downwardly through the jacket.It will be apparent that the air descending through the jacket in anannular curtain has intimate contact with the descending cascade ofliquid and passes repeatedly therethrough. This causes evaporation of aportion of the liquid and the resulting cooling effect causes heat to beremoved rapidly from the inner cover and the charge enclosed thereby.Neither the liquid nor the air have direct contact with the inner coverproper. This avoids excessive oxidation of the inner cover which wouldotherwise occur because of its high initial temperature. The innercover, nevertheless, is directly subject to the cooling effect resultingfrom evaporation of the liquid.

After the charge has been reduced to a temperature of say 500 F., thewater supply for the spray head 3| may be turned on to deliver a coolingspray in direct contact with the inner cover I The inner cover, however,will have a longer life if the cooling jacket alone is relied on toabstract heat from the charge, instead of apply.- ing cooling liquiddirectly to the inner cover. After the charge has been sufficientlycooled, the cooling jacket and inner cover are removed and then thecharge itself.

Our invention contemplates the delivery of a large volume of air throughthe jacket and the supply of sufiicient cooling liquid to make thedescending shower or curtain substantially continuous, circumferentiallyof the jacket. A cooling jacket for an inner cover adapted toaccommodate strip from 60" to wide should have a motor and fan capableof delivering approximately 100,000 cubic feet of ai per hour.

A modified form of cooling jacket I0 shown in Figure 3 is adapted forcooperation with a furnace base such as that shown in Woodson Patent2,137,869. In the construction shown in that patent, the radiant heatingtubes are mounted on the inside of the outer cover, the inner cover I!comprising simply an enclosure fabricated from plate adapted to bedisposed over the charge l3 resting on the base I2. The jacket I0 isgenerally similar to the jacket I0 except that the bottom of the innerwall 2| flares outwardly to form a generally horizontal flange 42. Theouter wall l8 has a bottom annular flange 43. The flange 42 has adepending annular wall 44 adapted to enter a sealing channel 45 on thebase and is provided with holes 46 for the escape of the liquiddischarged downwardly through the jacket. The inner cover I! also has adepending annular wall 41 entering the channel 45 and an annularsupporting wall 48 spaced inwardly therefrom adapted to rest on thebottom of a second channel 49. When the jacket I0 is in position overthe inner cover, the flange 42 thereof rests on the upper edge of theouter wall of the sealing channel 45. Other parts of the modifiedconstruction are similar to corresponding parts of the jacket is and aredesignated by similar reference numerals with a prime afiixed. Thejacket l functions in the same manner as the jacket IE! to produce rapidcooling of the charge within the inner cover I l.

The advantages of our method and apparatus for annealing have alreadybeen mentioned briefly. The strong cooling effect obtained by partialevaporation of the descending shower or curtain accelerates the coolingof the charge so that the time required for cooling it to a temperatureat which the inner cover may be safely removed is only about half thetime required for cooling by atmospheric convection. This saving of timeis directly reflected in the over-all cost of annealing since it makespossible an increase in the production obtainable with a given number offurnace bases or permits the same production to be obtained With asmaller number of bases. The structure of the cooling jacket is simpleand inexpensive and the use thereof does not require any special skillor training.

Although we have illustrated and described only a preferred practice andtwo embodiments of our invention, it will be understood that changes inthe construction and operation disclosed may be made Without departingfrom the spirit of the invention or the scope of the appended claims.

We claim:

1. Cooling apparatus for use with a cover-type annealing furnaceincluding a charge-supporting base and a protective cover enclosing acharge on the base. said apparatus comprising an openbottomed jacketadapted to be disposed over said cover and including spaced inner andouter'walls. means delivering a curtain of cooling liquid downwardlywithin the outer wall into the space between said walls, and means forcausing a flow of gas along the path of the liquid, thereby cooling saidcharge by evaporation of a portion of the liquid.

2. Cooling apparatus for use with a cover-type annealing furnaceincluding a charge-supporting base and a protective cover enclosing acharge on the base, said apparatus comprising an openbottomed jacketadapted to be disposed over said cover and including spaced inner andouter walls, means delivering a curtain of cooling liquid downwardlywithin the outer walls into the space between said walls, means forcausing a flow of gas along the path of the liquid, and bafiies in saidspace effective to cause intermingling of the liquid and gas.

3. Cooling apparatus for use with a cover-type annealing furnaceincluding a charge-supporting base and a protective cover enclosing acharge on the base, said apparatus comprising an open-bottomed jacketadapted to be disposed over said cover and including spaced inner andouter walls, means delivering a curtain of cooling liquid downwardlywithin the outer wall into the space between said walls, means forcausing a flow of gas along the path of'the liquid, a baffle wallintermediate said inner and outer walls terminating short of the bottomof the jacket and providing an annular passage for upflowing gas, andgas outlets in said outer wall.

4. Cooling apparatus for use with a cover-type annealing furnaceincluding a charge-supporting base and a protective cover enclosing acharge on the base, said apparatus comprising an open-bottomed jacketadapted to be disposed over said cover and including spaced inner andouter walls, frusto-conical bafiles spaced vertically of the outer wall,adjacent bafiies being oppositely disposed, and means for supplyingcooling fluid to the upper region of said space for downward flowtherethrough.

5. Cooling apparatus for use with a cover-type annealing furnaceincluding a charge-supporting base and a protective cover enclosing acharge on the base, said apparatus comprising an open-bottomed jacketadapted to be disposed over said cover and including spaced inner andouter walls, frusto-conical baffles spaced vertically of the outer wall,adjacent baffles being oppositely disposed, and means for supplying acascade of cooling liquid descending over said baflies.

6. Cooling apparatus for use with a cover-type annealing furnaceincluding a charge-supporting base and a protective cover enclosing acharge on the base, said apparatus comprising an open-bottomed jacketadapted to be disposed over said cover and including spaced inner andouter walls, frusto-conical bafiies spaced vertically of the outer wall,adjacent baflies being oppositely disposed, means for supplying coolingfluid to the upper region of said space for downward flow therethrough,and means for blowing gas through the fluid repeatedly to evaporate aportion of the liquid.

'7. Cooling apparatus for use with a cover-type annealing furnaceincluding a charge-supporting base and a protective cover enclosing acharge on the base, said apparatus comprising an open-bottomed jacketadapted to be disposed over said cover and including spaced inner andouter walls, means delivering a cascade of cooling liquid downwardlyinto the space between said walls, and means for causing a flow of gasthrough said cascade, means carried by said jacket for delivering acooling spray onto the top of the inner wall and means within the jacketfor delivering a spray onto said cover.

8. Cooling apparatus for use with a cover-type annealing furnaceincluding a charge-supporting base and a protective cover adapted toenclose a charge on the base, said apparatus comprising an open-bottomedcooling jacket adapted to be disposed over the cover, a distributor coneadjacent the top of the jacket, means delivering cooling fluid onto saidcone and means discharging a blast of air toward the vertex of saidcone.

9. Cooling apparatus for use with a cover-type annealing furnaceincluding a charge-supporting base and a protective cover adapted toenclose a charge on the base, said apparatus comprising an open-bottomedcooling jacket having spaced inner and outer walls and adapted to bedisposed over said cover, a distributor cone extending over the upperedge of the inner wall, means delivering cooling fluid onto said coneand means for discharging a blast of air toward the vertex of the cone.

10. A cooling jacket for an annealing cover comprising an open-bottomedcylinder, a distributor cone in the cylinder near the top, a fan blowingair onto the cone and a cylindrical baffle spaced inwardly of the jacketcylinder and terminating above the lower edge thereof.

ALFRED E. ALLEN. JAMES L. WHITTEN.

